1Department of Chemistry, Organic Chemistry, The Group of Ecological Chemistry, The Royal Institute of Technology, 100 44 Stockholm, Sweden.
2Mid Sweden University, Department of Chemistry and Process Technology, 851 70 Sundsvall, Sweden.
3Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, 166 10 Praha, The Czech Republic.
4Department of Entomology, Swedish University of Agricultural Sciences, P.O. Box 7044, 750 07 Uppsala, Sweden.
5Norwegian Forest Research Institute, Forest Ecology, Høgskoleveien 12, 1432 Aas, Norway.
The aim for this study was to analyse the chemical diversity of monoterpenes in six species of pine and to correlate the host selection of, and susceptibility to, forest insects such as Tomicus piniperda and Hylobius abietis. In addition, the influence of fungi infections, by inoculation of Leptographium wingfieldii and Ophiostoma canum, to the monterpene composition in the phloem of P. sylvestris was determined. Relative amounts and enantiomeric compositions of the monoterpene hydrocarbons in branch and trunk xylems, in needles and in resin from apical buds in Pinus sylvestris trees were investigated. The composition of monoterpenes in branch xylem in P. sylvestris was found to be very similar to the one in trunk xylem, while there were large differences in the relative amounts among xylem, needles and oleoresin. Correlation plots of monoterpene enantiomers, based on selective normalization, can provide information about the biosynthetic routes of monoterpenes. The monoterpene hydrocarbons in the trunk xylem of P. sylvestris, P. caribaea, P. cubensis, P. tropicalis, P. yunnanensis and P. armandii were compared in order to investigate taxa specific patterns. Clear correlations between (+)-alpha-pinene and (+)-camphene were found in the trunk xylem of P. sylvestris, P. cubensis, P. yunnanensis and in P. caribaea, but no correlations in P. armandii. The correlation found between (-)-alpha-pinene and (-)-beta-pinene in P. yunnanensis, P. tropicalis and to some extent in P. caribaea was absent in P. sylvestris and P. armandii. Thus, the expression of monoterpene synthases seems to differ among species.